Quote:
Originally Posted by G0HZU_JMR
There's lots of ways to generate the signals, including a 74HC4060 and crystal(s).
However, as you will be running the transmitter right next to the receiver I would recommend running the signal source at twice the frequency (continuously) but key a flipflop divide by two (74HC74?) as the morse sender ahead of the final stage and LPF. That way, there will be 'nothing' heard in the receiver in the gaps between morse characters, i.e. no constant low level leakage tone if the transmitter is right next to the receiver. Otherwise, you would have to screen the low level stages of the transmitter very well in order to avoid a constant leakage tone appearing in the background in the receiver.
The alternative is to key the oscillator on and off but that will probably sound a bit chirpy and unpleasant.
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I would also suggest the use of crystals and a divide by n chip, as you can then use a crystal around , say, 5120kHz which are quite plentiful and divide that down to 512kHz. I did a similar mod to a Marconi Commandant to get LSB on it and needed a crystal around 100kHz.
HTH
Roger